Comparative in vitro and in vivo studies of the antigenic composition and growth properties of rodent cells derived from normal and neoplastic adult liver tissue will be carried out. The occurrence of fetal and ectopic antigen expression, as determined by immunochemical methods, will be correlated with the degree of hepatocellular pathology observed and the in vitro growth properties of liver-derived cells. The usefulness of the expression of a sppcific ectopic antigen (gamma-fetal antigen) as an immunodiagnostic antigen will be evaluated. Experiments concerning the potential modulation of ectopic antigen expression by the IgG fraction of anti-gamma-fetal antigen serum, or the Fab fragments prepared therefrom, may elucidate specific associations between ectopic antigen production and the process of neoplastic transformation.